1. Field
The following description relates to holographic three-dimensional (3D) printing apparatuses and methods of driving holographic 3D printing apparatuses.
2. Description of Related Art
As interest in three-dimensional (3D) stereoscopic images has increased, devices configured to display such stereoscopic images have been developed. Since high resolution stereoscopic images having a natural appearance may be made using holography, holographic 3D printing apparatuses have also been actively studied.
Holographic 3D printing apparatuses record 3D image information on a holographic recording medium, which is a photosensitive storage medium, as an interference pattern. An interference pattern is formed when a reference beam emitted from a light source interferes with a signal beam emitted from the light source. The interference pattern is recorded on a holographic recording medium by chemically or physically changing a holographic recording medium. When a holographic 3D printing apparatus is used to emit a reference beam to the holographic recording medium on which the interference pattern is recorded, a 3D stereoscopic image is reproduced from the holographic recording medium. Such holographic 3D printing apparatuses may be applied to holographic displays and stereoscopic image output devices used in homes or offices.
FIG. 1 is a plan view illustrating a general example of a holographic three-dimensional (3D) printing apparatus. Referring to the example illustrated in FIG. 1, a beam emitted from a light source 10 is split into a reference beam R and a signal beam S by a beam splitter 20. In an example, the light source 10 is a laser source for emitting a pulse laser beam. In another example, the beam splitter 20 is a polarizing beam splitter.
The signal beam S obtained by the beam splitter 20 is expanded while passing through a phase mask 31 and a predetermined lens 32. The expanded signal beam S passes through a collimating lens 33 and an illumination unit 34 and, thereafter, becomes incident on a spatial light modulator (SLM) 35 on which predetermined color information is displayed. The signal beam S modulated by the SLM 35 passes through an objective lens unit 36 and is emitted to a holographic recording medium 50. In an example, the illumination unit 34 is a polarizing beam splitter. In another example, the objective lens unit 36 is a Fourier objective lens.
The reference beam R obtained by the beam splitter 20 passes through a first reflection mirror 41, a lens 42, and a second reflection mirror 43, and is thereby emitted to the holographic recording medium 50. Accordingly, the signal beam S interferes with the reference beam R on the holographic recording medium 50 to record an interference pattern.